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PubMed1994

Comparative analysis of tetanus antitoxin titers of sera from immunized mice and guinea pigs determined by toxin neutralization test and enzyme-linked immunosorbent assay.

Enzyme-linked immunosorbent assay (ELISA) and toxin neutralization (TN) test were comparatively evaluated for determination of antibodies to tetanus toxin in sera of immunized guinea pigs and mice at different intervals. Tetanus specific IgG antibodies by ELISA were found in sera of guinea pigs at ninth day after inoculation and in mice sera at seventh day after inoculation when there were no TN antibodies. Two weeks after injection of mice with aluminium phosphate adsorbed tetanus toxoid, anti-tetanus toxin IgG levels determined by ELISA were 35 to 40 times higher than the TN titers. At 4 weeks, ELISA IgG antibody levels of mice and guinea pig sera were still statistically significantly higher than TN titers but with a good correlation between ELISA and TN titers (correlation coefficient of mice sera 0.89). Mice sera at 2 weeks after two doses of tetanus toxoid (interval between doses 30 days) and 8 weeks after a single injection showed similar ELISA and TN titers (P > 0.1). Guinea pig sera at 6 weeks after a single injection showed similar TN and ELISA titers (P > 0.4). During the course of immunization in mice and guinea pigs, low avidity and low affinity IgG antibodies start appearing early which are detected by ELISA but not by TN test. Therefore ELISA results on sera before 6 weeks of immunization determined against a hyper-immune reference serum do not give a true picture of TN levels.

Animals↗
PubMed1981

Immunological relationship among adenoviruses of humans, simians, and nonprimates as determined by the neutralization test.

98 antisera prepared against 25 simian adenoviruses and 31 adenovirus types from various nonprimate mammals and birds were tested for their ability to neutralize 35 human adenovirus prototypes. Antisera to these human adenovirus types were similarly tested against 25 simian adenovirus prototypes. Although very few reactions to the human adenoviruses were found in antisera to nonprimate viruses, cross-reactions among the simian and human adenoviruses were more frequent. The majority of these reactions, however, were of low titer and of questionable significance. Two chimpanzee adenovirus strains--Pan 9 and SAV 21 (C 1)--were found with an immunological relationship to human adenoviruses: Pan 9 strain showed a two-way cross relationship to human adenovirus 4, and SAV 21 (C 1) was neutralized by antisera prepared against human adenoviruses 14 and 16.

Adenoviridae↗
PubMed1967

Serology of rubella. Comparison of fluorescent antibody, complement fixation and neutralization tests for diagnosis of current infections and determination of sero-immunity.

Neutralization, complement fixation (CF) and indirect fluorescent antibody (FA) assays for rubella virus were compared for sensitivity in the serologic diagnosis of infection, for demonstrating antibody in the sera of infants with suspected rubella syndrome, and in the detection of antibody elicited by past infection (determination of immunity status). The combination of CF and FA tests was shown to be the most useful for serologic diagnosis of infection, largely eliminating the need for the slower and more cumbersome interference neutralization test.Neutralizing antibodies were found to appear rapidly in the course of infection, antibodies demonstrable by immunofluorescent staining appeared slightly later, and CF antibodies were rarely demonstrable in sera collected earlier than 14 days after onset of illness. Antibodies detected by all three techniques showed good correlation in infants with clinical evidence of rubella syndrome and corresponding maternal sera. The indirect FA technique compared favorably with the neutralization test for the detection of antibody elicited by past infection (determination of immunity status) and offered distinct advantages in ease of technical performance and more rapid results. In both current and past infections, FA titers tended to be higher than neutralizing antibody titers.

Complement Fixation Tests↗
PubMed1993

Reappraisal of modified neutralization test for Inoue-Melnick virus.

Ito et al. (1992) reported an improved modification of the neutralization (NT) test for Inoue-Melnick Virus (IMV) by prolonged 90 min incubation of the mixture of the virus and serum. For confirmation, we compared the results of the NT test by 90 and 60 min incubation. Against human sera, the NT test by 90 min incubation was significantly more sensitive than the test by 60 min incubation. By 90 min incubation, the NT titers increased by 3 to 6 times and approximately 6% of antibody-negative adult sera previously determined in the tests by 60 min incubation turned to positive (more than 1:10). However, antibody-negative sera of Japanese children examined previously in the tests by 60 min incubation remained negative after the 90 min tests. On the other hand, against rabbit immune sera, no significant difference of NT titers was observed between the two NT tests for 90 and 60 min incubation. Also we reinvestigated Japanese adult sera for type 2 IMV infection by the NT test for 90 min incubation, but did not find any serum of type 2 or intermediate type infection. Therefore, it is not necessary to change the previous conclusion that in Japan IMV infections are mostly of type 1.

Animals↗
PubMed1989

A rapid serum neutralization test in microplates for the detection of antibodies to hog cholera virus.

The fluorescent antibody serum neutralization (FASN) test for the detection of antibodies to hog cholera virus was developed utilizing 96-well and Terasaki microplates. This microtechnique, especially when performed in Terasaki plates, offers some advantage if compared with conventional FASN in coverslip cell cultures, being easier and more rapid, saving of reagents and allowing simple microscopic observation.

Animals↗
PubMed1990

Comparison between results of virus neutralization test and those of two ELISAs when screening for antibodies to pseudorabies virus in Thailand.

The virus neutralization (VN) test and two enzyme-linked immunosorbent assays (blocking and indirect ELISAs) were used to detect antibodies to pseudorabies virus on serum samples of 1,000 pigs from the central part of Thailand. The results of these tests were compared to those of VN test. Using the VN test as standard, the blocking and indirect ELISAs showed respectively 95.12% and 99.37% relative sensitivity and 92.0% and 93.5% relative specificity. The two ELISAs were considered both as practical alternatives to the VN test. However, the indirect ELISA was the more suitable test for the routine screening for antibodies to pseudorabies virus in Thailand.

Animals↗
PubMed1969

A serum neutralization test for infectious bovine rhinotracheitis based on colour reaction and cytopathic effects in cell culture.

A serum neutralization (SN) test based on a combination of indicator colour change in medium and cytopathic (CP) effect in cells has been devised for the detection of infectious bovine rhinotracheitis antibodies. Serum dilutions of 1:6, 1:18 and 1:54 are made in a medium containing phenol red and are mixed in equal quantities with a suspension of virus containing 100 cell culture infectious doses (CCID(50)) per volume of mixture. The serum-virus mixtures are held in small glass tubes and are covered with a layer of mineral oil. Following a two hour period of incubation at 37 degrees C a quantity of bovine fetal kidney cells is added to each tube to detect the presence of unneutralized virus. After four to six days incubation the results of the SN test may be read by microscopic examination for CP effect by means of an inverted microscope, or by observing the colour of the phenol red.

Culture Techniques↗
PubMed1988

Reevaluation of the western equine encephalitis antigenic complex of alphaviruses (family Togaviridae) as determined by neutralization tests.

Fourteen viruses closely related to the Fleming strain of western equine encephalitis (WEE) virus were cross-tested by serum dilution-plaque reduction neutralization. The results demonstrate that strains McMillan, R-43738, AG80-646, BeAr 102091, and Y62-33 are subtypes or varieties of western equine encephalitis virus strain Fleming. Ockelbo, Kyzylagach, and Babanki are subtypes of the prototype strain (EgAr 339) of Sindbis virus. Fort Morgan and Buggy Creek viruses are closely related to each other, whereas Highlands J and Aura viruses are distinct from other members of this antigenic complex. There appear to be parallels between geographic distribution and antigenic relatedness. We hypothesize that birds, the principal vertebrate hosts for these viruses, spread the progenitor viruses north and south and from continent to continent. Viruses of the WEE complex with lesser antigenic differences may develop in discrete ecologic conditions.

Alphavirus↗
PubMed1988

Cross-neutralization tests among Cache Valley virus isolates revealing the existence of multiple subtypes.

Maguari virus has been classified as a subtype of Cache Valley virus. Seven Bunyamwera serogroup viruses (including prototypes Cache Valley and Maguari viruses), 4 viruses shown in previous tests as close antigenic relatives of Maguari or Cache Valley viruses, and Xingu virus were cross-tested by serum dilution-plaque reduction neutralization. All viruses were distinguishable from prototypes Cache Valley and Maguari viruses. The close antigenic relationships of the Cache Valley-like viruses demonstrate that multiple subtypes of Cache Valley virus exist and suggest that such antigenic variation is a phenotypic expression of considerable genetic diversity.

Antigens, Viral↗
PubMed1996

An enzyme immunoassay based micro-neutralization test for titration of antibodies to human cytomegalovirus (CMV) and its correlation with direct ELISA measuring CMV IgG antibodies.

An ELISA-based micro-neutralization (Nt) test in MRC-5 cells for titration of neutralizing antibodies against human cytomegalovirus (CMV) in human plasma and preparations of immune globulins was developed to eliminate microscopic reading of cytopathic effect (CPE), a process that is subjective and time consuming. Un-neutralized CMV from the Nt reaction and grown in MRC-5 cells as per the standard micro-Nt test was coated in the same plates by various methods and CMV antigen was quantified by polyclonal or monoclonal CMV antibodies. Optimal coating of plates with CMV antigen (100 TCID50 of virus grown on MRC-5 cells for 7 days) was obtained by freezing/thawing of virus infected MRC-5 cells in phosphate buffered saline, ph 7.2. The CMV antigen treated sequentially with CMV monoclonal antibody to late nuclear protein antigen, goat anti-mouse IgG3 alkaline phosphatase conjugate and phosphatase substrate gave an absorbance of 1 at 410 nm wavelength whereas uninfected MRC-5 cells treated under similar conditions did not show any absorbance. The optimal Nt reaction occurred at 37 degrees C for 1-2 h and was unaffected by complement. At 4 degrees C, CMV was inactivated in 1-2 h. The antibody titres were affected by the virus dose used in the Nt test over a range of 20 to 798 TCID50. When the titre was determined against a reference serum, the effect of virus dose on the Nt titre was reduced. Complete neutralization virus read microscopically correlated with ELISA absorbance of < 0.1. CPE produced by approximately 1 TCID50 of CMV showed an absorbance of 0.1 or more. The correlation coefficient (r) between Nt titres and CMV IgG antibodies determined by ELISA was 0.69 (P < 0.001) for 257 human plasma samples and 0.85 (P < 0.001) for 50 immune globulin preparations.

Antibodies, Viral↗